WO 94/08230 describes a method and a device for inspecting transparent containers and their liquid contents. The disclosed device has two continuously drivable carousels; the containers that are to be inspected, e.g., filled beverage bottles, pass through these carousels one after the other. In the first carousel as seen in the direction of conveyance, the containers are first rotated once completely about their vertical axis at a low rate of rotation, during which the side wall is observed by a camera for detecting damage or other defects in the container itself. Following this, the rate of rotation is initially increased to induce rotation of the liquid with the goal of creating turbulence to churn up any foreign bodies present on the bottom of the container. Even before leaving the first carousel, the rotational movement of the containers is stopped so they can then be transferred via a first star wheel, a pitch lag screw and a second star wheel to the second carousel, where the containers are inspected by a bright field method and also by a dark field method by cameras that move with the carousels but without any rotation of the containers themselves about their vertical axis in order to detect any foreign bodies in the filling of the containers (suspended materials, particles, etc.).
One disadvantage is that a separate, independently controllable electric motor drive is provided for each container in the first carousel, but this is very high expensive in terms of the drive technology.
Another disadvantage is that the transfer zone from the first carousel to the second turns out to be very long due to the use of the two transfer star wheels with the screw connected in between; this results in a relatively great deceleration of the rotating liquid in the containers even before reaching the second carousel, where the actual foreign body detection in the liquid is then performed. However, the reliability of this inspection method is inadequate at low throughput rates and/or with heavier foreign body particles, in particular transparent bodies, which can be detected reliably only when in movement.
In addition, the conveyance elements mentioned above, which are necessary for the intermediate transfer, depend on the format of the containers to be inspected and must therefore be switched to another type of container with each conversion of the inspection machine [from one product to another]. This is also true of the intake star wheel of the first carousel and the output star wheel of the second carousel. Furthermore, the guide curves arranged between the star wheels are also interchangeable parts that depend on the format.
Because of the great center-to-center distance between the two carousels, the known inspection machine also takes up a relatively large amount of space.